Travel: Planes, Trains, and Germs (cont.)

SARS and influenza, of course, are only two of the multitude of bugs lurking
out there. But the case of Flight 112 suggests that the current understanding of
the spread of airborne disease aboard aircraft, which is based on tuberculosis
investigations, may be outdated. Emergency medicine specialist Mark A. Gendreau,
MD, senior staff physician at Lahey Clinic Medical Center, Burlington, Mass.,
recently reviewed what is and isn't known about infectious disease spread during
air travel.

"The CDC and World Health Organization say you risk getting an infection only
if you are sitting within two rows of someone who has something - and only if
you are sitting there for more than eight hours," Gendreau tells WebMD. "But
Flight 112 was only three hours long, and people sitting as far as seven rows
back were affected. So that says, 'Wait a minute folks.' That old advice may
have worked for tuberculosis, but what about SARS and other infectious diseases?
More study into that is needed."

There's a lot we don't know, agrees Roy L. DeHart, MD, MPH, senior consultant
in occupational and aviation medicine at Vanderbilt University, Nashville, Tenn.
And if anyone understands the various health risks of flying, it's DeHart. He
capped his 23-year Air Force career as commander of the USAF School of Aerospace
Medicine. Former director of occupational and environmental Medicine at the
University of Oklahoma, he's an FAA-certified senior aviation medical examiner.

"We don't know what that passenger next to you is contributing to the air
stream as he is inhaling and exhaling," DeHart tells WebMD. "With flights coming
out of developing countries where prevention programs are not as strong as they
might be, it is not unusual that a person may have a problem like tuberculosis.
It spreads. Usually just to two or three people, but if a patient is found on
board, health authorities have a tough job trying to track those people down. It
can be a horrendous problem. There can be hundreds of patients spreading
whatever, wherever. Major spread is possible. So, yes, there can be problems."

Which Is Healthier: High-Flying Planes or High-Rise Offices?

Air passengers often complain about aircraft ventilation. But Gendreau notes
that a normal airplane cabin changes its air 15 to 20 times an hour. A typical
office building changes its air 12 times an hour.

High efficiency particulate air (HEPA) filters scrub the air on some planes.
The filters may be able to trap airborne viruses because they catch the droplets
that carry the viruses. But 15% of U.S. commercial airliners carrying more than
100 passengers lack HEPA filters.

"Federal regulatory agencies need to tighten the rules in terms of
ventilation and in terms of the HEPA filters that are used," Gendreau says.
"Now, in the U.S. and Europe, there are no requirements for how much ventilation
an aircraft should have. They don't specify what kind of HEPA filters to use -
or even require them."